'morning ARC, would like to explore sanding
substrates: 2 in mind, wood -> varnish
the wood will always be a hardwood and with years of drying before use (have a bodega full of wood)
the varnish will always be an exterior 'polyurethane' (assuming I can find) sanded . . . .
ok, sanding wood is straight forward and I generally use 60/80, 150 if I'm being prissy, and 220 all with a 5" orbital sander
I will then hand-sand with 600 grit as posted above.
I have found that varnishing a 220 sanded surface simply leaves more material to be removed later with 600 grit.
sanding green resin can be quite difficult, have far better results with the Norton paper
the transition from a wood substrate to built-up varnish is somewhat gradual,
a single thinned coat will not completely seal and must in any case be sanded (my huge error was going for thick coats !)
the manner and extent of sanding between coats seems most tricky
you (and others) recommend steel wool, others not because of a crazing effect
- but I have seen crazing also over a sanded area due to a too-thin resin mix replicating the substrate below it
the ss wool would seem to lack any leveling capability whereas paper can be fitted to a soft block
why is the ss wool better ?